1. Field of the Invention
The invention relates in general to a communications device, and more particularly to a wireless communications device and a method of radio control adapted therefor.
2. Description of the Related Art
In a network device, two radios are increasingly preferred over one radio in order to improve quality of link and service, and to expand functionality in networking. For instance, user can have two radios be used as access points to enhance throughput and latency; or have one radio be used as an access point and have another be dedicated to operate as monitor for site surveying or operate as bridge or wireless distribution service for backhauling. However, the inherent problem with a co-located two-radio system is the interference of one radio to another.
There are several causes for interferences of in-band or out-band frequencies. One can be attributed to sidelobe interferences. That is, the sidelobes of one channel, fall in the in-band adjacent or alternative channels and interfere with another carriers operating therein. Another cause of interference is due to third order intermodulation, in which the fundamental frequency of a signal and the second harmonic of aother signal result in frequency mixing. A third cause of interference arises from the interference of the second harmonic of a signal in a band with other signals out of the band. Hence, channel isolation is required to prevent interferences.
Non-adaptive antenna and radio screening method has been proposed to provide isolation between channels. Interferences are mitigated using extremely non-overlapped channels, such as ch. 1 and ch. 11 for a IEEE 802.11g standard, with very broad guard-channel therebetween. Interferences are also lowered using wide separated antennae, with very broad guard-spacing therebetween.
The non-adaptive method in common guard and attenuation solely provides the purpose of screening, and is yet to provide a satisfactory result towards reducing interferences. However, the conventional method poses limitation towards the allowed spacing between two operating channels and between two antennae, thereby reducing flexibility.